pH sensor based on AuNPs/ ITO membrane as extended gate field-effect transistor

In the present work, gold nanoparticles/indium tin oxide (AuNPs/ITO) thin films were analyzed for pH sensing application based on extended gate field-effect transistor (EGFET). The AuNPs were synthesized through pulsed laser ablation in liquid (PLAL) technique. Afterwards, the AuNPs were deposited onto ITO thin film by electrospinning method. The AuNPs were characterized using transmission electron microscope (TEM) and UV-Vis spectroscope techniques. From the TEM analysis, the size of the spherical-shaped AuNPs was found to be in the range of 5-22 nm. The UV-Vis spectroscopy analysis revealed absorption peak at 518 nm, indicating purplish red color. The AuNPs/ITO thin films were also characterized using field emission scanning electron microscope (FE-SEM) and X-Ray Photoelectron Spectroscopy (XPS) technique. The depth of the films was 6.498 mu m and the Au 4f doublet binding energy peaks of the photoelectrons at 83.79 and 87.45 eV. The current-voltage (I-V) curves indicated pH sensitivities values of 43.6 mV/pH and 0.6 mu A(1/2)pH(-1) with linear regression of 0.99 and 0.99 for pH voltage and current sensitivities, respectively. The hysteresis and drift characteristics of the prepared films were also done to investigate the stability and reliability of the films. The results of this work demonstrated that the AuNPs/ITO thin film is quite useful for the acidity and basicity detection.